Category: Mono

I was asked by Packt Publishing if I would read and review this book. I’ve owned a BeagleBoneBlack for a little while now. My use case was not robotics. This book might shed some new light on my old Black, so I agreed to review it.

The book starts off very accessible. Chapter 1 covers just about everything I did with my BBB when I first received it, hooking it up like a PC, replacing the default distro, making sure I could SSH to it were all in there. The author, Richard Grimmett, goes a step further and installs XFCE gui and vncserver and walks through connecting from a Windows PC using vncclient. All in all, chapter 1 is a great super basic tour.

Chapter 2 dives into programming on the thing and introduces Python. It does it in a really weird (to me) way. It has the reader running emacs in a putty window remote connected to the device. This must just feel weird to me because I do a lot of remote programming and its never with emacs (I’m a vim guy) and its rarely remote. For a new user, it seems to me like it would have been simpler and more friendly to say “use an editor of your choice” and “here is notepad2 or sublime” along with “here is how you copy files to and from the device.” I think this is mostly my background causing me to see things differently. The emacs in putty walk-through is very adequate.

Its not a programming book, so this is really a nit pick, but technically some of the descriptions of python aren’t really true. For example, if __name__==”__main__”: does not “tell the program to begin its execution at this point.” Again I’m nit picking, but I do feel like a different phrase that isn’t so very false to someone who knows python could have been found. Still, its not a programming book. The beginning of the chapter does list many resources for learning python.

Ugh, and then the book moves on to C++ and has quotes like this, “C++ is the original language of Linux” I’ve used Linux for almost as long as I’ve programmed C, and I am very (perhaps overly?) sensitive to the difference between C and C++.

OMG what do you mean Speech Input and Output? Really? Chapter 3 tackles it. Really. For real. Speech Input and Output on that tiny little board. I can make my own Siri! This is a really cool topic; espeek is something I’ve only played with a little bit prior to reading this. It looks fun.

Speech recognition is done with software I’ve never used before called PocketSphinx. It isn’t packaged and so one has to compile it. Pretty sweet BBB being able to compile stuff like that. (I’m thinking of iOS and Android where I’ve not seen a compiler run on device.) The demo walks through limiting the grammar of speech input so that you don’t have to train the recognizer.

I’m a programmer, so I’m going to nitpick programmer things. I really wish authors wouldn’t do this, “I like to make a copy of the current file into continuous.c.old, so I can always get back to the starting program if it is required.” I really do wish authors would just say “go read about version control systems.”

Whew, speech is fun. Next step is video. Hook up a webcam and let’s do some image recognition. The book walks through OpenCV and it is as this point that we are forced to do a bunch of Linux sysadmin stuff to make our SD have enough free space to have a dev environment. This really could have gone anywhere in the book. I kind of like that it put it off until it was necessary.

The python image tracking example using OpenCV looks pretty cool. It is a complete example without going too deep or going off in the weeds.

Making the Unit Mobile introduced me to mobile platforms. The Magician Chassis that the book shows first, I found online for under $20! I knew that this stuff was accessible, but this is downright cheap. I feel almost guilty NOT getting one and trying it out.

The motor controller tutorial looks very straightforward. I already have ideas for code changes. Immediately after the simple time based tutorial it goes into speech controlled movement, which is pretty sweet.

After the wheeled robot tutorial is a walking robot example. The author makes a compelling argument for this type of robot, and the Pulse Width Modulation servo motors are cool, but I have to admit, this type of robot just doesn’t excite me. The book also punts on the PWM, using a controller which interprets serial USB commands into the PWM for the servos. For beginners, this is certainly the right choice.

Incidentally, the –help output from UscCmd includes Version, Culture, PublicKeyToken values like a Mono program might. I wonder if it is written in C# and running via Mono. I’m going to assume it is. That is pretty sweet. Indeed the linked download page mentions C#. http://www.pololu.com/docs/0J40/3.b

The sonar sensors section is a straightforward and great introduction to the use of them. I never knew how those things worked or what kind of value they returned. Now I do. Mounting the sensor to a survo makes for a nice subsystem on the bot.

Next, a fully remote control system is built. I don’t know if I like the choice of using an LCD monitor. It seems like overkill, but depending on the particular robotic application it would be a good choice. For the applications I have in mind, I think I’ll skip it. A wireless usb keyboard and mouse makes for an obvious choice. At this point, I just keep thinking about bluetooth and using an extra Wiimote, mostly because I think it would be a more fun control.

Oh, a GPS receiver! This could be necessary for when I lose my robot in a parking lot or the woods. As with the LCD Monitor and KB chapter, I kind of feel like I know how to do this since I’ve looked into it before. It is great coverage and good intro to the topic.

Much of my day job is what would traditionally be called Systems Programming so Chapter 10 is kind of a duh to me. I’d have started there, but that is just how I think about coding these days. Its great to have this in a chapter to tie some things together. In other words, read this chapter!

Using the BBB in sea, air and submarine applications is an interesting idea. I don’t think it is for me yet, but the book gives introduction to some ideas on the topic. The introduction to feedback control is very welcome.

Overall this is a great book. It really gave me a lot of ideas. It also showed me how easy it is to get started, something which I’d been a little hesitant to do. I’m actually a little excited to dive in now. I’ll be doing a bunch of this stuff with my 6yo over the next few years.

I’ve been watching more FOSDEM videos. They are very cool. Watching in 720p is awesome.

Alan McGovern on The Evolution of MonoTorrent – By far the best bittorrent library for .net. Alan talks about the challenges of writing a library that will handle things like hundreds (if not thousands) of simultaneous socket connections, why using threads to do so is wrong, and how good design and the async pattern made it easy and fast.

Stephane Delcroix on Image Processing – I was really looking forward to this one – Mono.SIMD is awesome – but the whole thing is code and the non-bold small font on a white background did not get picked up by the projector. Needless to say that Mono.SIMD is still awesome, but the talk isn’t really worth watching. I’ll be it was cool live though. If you don’t know Mono.SIMD is yet another Mono innovation that is Mono-only. It provides an object oriented api for the underlying SIMD instructions in modern cpus. These are the SSE instructions that you see listed in the spec about your Core2 CPU.

Jeremie Laval on Parallel Fx – This is NOT just another talk on Parallel Fx aka Task Parallel Library+PLINQ. Jeremie actually wrote Mono’s implementation of TPL. While its great to see Stephen Toub show use cases of TPL, the geek in me wants to see what is under the hood. Jeremie gets into some of the challenges in implementing the scheduler and library. He also mentioned that .NET4’s thread pool actually uses the TPL scheduler underneath. I didn’t know that. He also shows a demo of Future<> which I had never considered. Chaining Future<>’s in a tree like manner in order to create parallel delayed evaluation.

Andreia Gaita on Moonlight and You – Why moonlight is important to mono? WOW! They are working on XAML designers for MonoDevelop. I can’t imagine how awesome moonlight development will be on Linux in the future. Moonlight is super close to working in Chrome on Linux. mxap –desktop lets you create moonlight desktop apps launchable with the mopen command. Very cool. Desktop apps in moonlight. Very cool pixel shaders on video in moonlight 3.

Jim Purbrick on Building The Virtual Babel – Mono in Second Life – The virtual worlds in Second Life and how it has progressed for 7 years. Very cool to hear how an existing language LSL and existing virtual machine was moved to a new virtual machine, Mono. I’ve never heard of JavaGoX or Brakes so listening to the description of script migration was rather mind blowing.(very cool)

Joe Shields on OSCTool – learning C# and Mono by Doing – While probably not of interest to a lot of developers, this one hit close to home for me because I was in a position pretty close to Joe’s about 8 years ago. Of course I didn’t know .NET at the time and Mono was still very young, but I do recall playing with some ASMX web services to do things similar to what he was doing. Joe makes a point that python, perl, C and even Java have cross platform difficulties (think HPUX, Itanium, Tru64 etc) of which Mono seems to mitigate much. The audio goes out for a few minutes in the middle, just skip to about 17:00 and watch the demo.

Mirco Bauer on Smuxi – IRC in a modern environment – Just an irc client with some special features. I’ll definitely be looking into this because I’m an IRC junkie, and it also has the exact twitter client that I’ve been looking for since I started using twitter.

As a .NET programmer in my day job targeting Windows desktop applications (winforms and wpf), I don’t get to stay on top of much ASP.NET or Mono. The ASP.NET stuff I feel like I have a good enough handle on via channels I use to stay on top of .NET in general (user groups, blogs, etc). Mono gets much less coverage there.

Luckily there are some awesome (720p quality) videos from FOSDEM 2010 of some Mono centric presentations.

Lluis Sanchez Gual on MonoDevelop – I knew MonoDevelop 2.2 had some awesome in it, but I didn’t know about some of the code generation things in it. Think R# mixed with CodeRush. It is very sweet. Lluis’s Blog is always a good read too.

Ivan Porto Carrero on IronRuby – Poor Ivan had some demo troubles, but overall the presentation was excellent. It is VERY cool to see a Banshee add-in written in Ruby. I don’t think I was reading Ivan’s Blog before, but I am now.

Miguel on Mono – I think this is kind of Miguel’s “State of the Monkey” of the day. Its a status overview with a few deep dives into things. I especially thought it was cool that he went deep (well, deeper than most) into Expression<>.

The videos seem to be coming out slowly. I’m posting these brief summaries of the videos as I watch them, so expect me to link to more as I watch them.

F.cs(334,8): error CS0539: ‘I.M’ in explicit interface declaration is not a member of interface F.cs(20,15): error CS0535: ‘C’ does not implement interface member ‘I.M(out string)’

This is a fun example of a poor error message, and I don’t mean because I named my file F, my interface I, my method M and my class C.

Its poor because the underlying code looks like this:

interface I { bool M(out string); }

class C:I { void M(out string); }

Sure, this is obvious now what is going on, I have void, but I should have bool, but my error message doesn’t include that when it shows the type signature. Now consider what happens when interface I is in an assembly which is given to me. I do not have its source, and there is no documentation. My means of finding the signature of this method are three fold:

lean on visual studio press F12 to go to reference of the interface and VS shows me type signatures

use reflector

monodis mylibrary | grep MethodName

I usually use #1, which is probably why I’ve never seen how horrible this compiler error message is until today. Today, I used #3.

I run my own DNS in our home. You may think this is crazy, but test after test has shown that nearly all ISPs provide substandard DNS to their customers. Even the finest DNS servers are only responsive 95% of the time. With the number of times you use DNS, you could be losing seconds or minutes per day while you wait for timeouts and rerequests.

Mvps.org maintains a list of “known bad domains”. While it is certainly not a replacement for other security measures, its another line of defense. It is another tool in the bag. For more reasons, read their site.

I don’t want to maintain host files on all of my home systems and all of the VMs too, I’d like to just tell my DNS server about these hosts and have it do the right thing.

By combining the downloaded hosts file and using this little boo script to map it into bind config, I have done just that. I use include files to bind. I’ve added a line like this to my /etc/bind/named.conf.local on my ubuntu server

include "/etc/bind/named.conf.mvps";

Then, I’ve added the output of this boo script to the /etc/bind/named.conf.mvps file. Reload bind and everything is done.

In my last post I showed how to build Mono trunk on the latest Ubuntu. I pointed out that I am using it on a “server” install of Ubuntu. I don’t have GTK+ or GTK# installed. So what good is Mono? Its good for hosting ASP.NET web applications.

With the release of Ubuntu 9.04 aka Jaunty later this month, I thought I’d share how to get a current version of Mono on the latest Ubuntu release.

For a number of reasons, Ubuntu always seems to be just a little behind current with its Mono packages. The largest reason IMO is the difficulty in properly packaging Mono for Debian/Ubuntu. I’ve tried and it is not easy.

Install the old Mono 2.0 C# compiler from jaunty so that we can bootstrap the trunk compiler. sudo apt-get install mono-mcs ln –s /usr/bin/mcs1 /usr/bin/mcs This installs enough mono to let the C# compiler run. We will remove this and all its dependencies later.

Fetch the source from SVN. I use a mono-dev-update script to checkout the first time and keep me updated. The script pulls and installs mono, mcs, xsp to /opt/mono on a default ubuntu server install once step 1 above has been performed. To build more parts of mono such as GTK# and MonoDevelop you will need more gtk+ library dependencies. sudo mkdir –p /opt/mono/src sudo chown $USER /opt/mono /opt/mono/src ./mono-dev-update